Question

20. Find a formula for the length of a room in terms of its
brcadth, b metres, and the perimeter of its floor, P metres.
​

Answer 1

Step-by-step explanation:

Let l, b and h be the length, breadth and height of the room.

The four walls of the room are to be painted.

Area of the two walls containing the length =2lh

Area of the two walls containing the breadth =2bh

Total area of four walls=2lh+2bh

=h×2(l+b)

But 2(l+b) means the perimeter of the floor of the room.

Total area of walls =25×h sq.m. ....(i)

Total area of walls =

Rate of painting

Total cost of painting

=

10

750

Total area of walls=75sq. m. ...(ii)

Equation (i) = equation (ii)

25h=75

∴h=3m

Thus, the height of the room is 3m.